A parking brake to lock a wheel while a vehicle is in a parking state has conventionally been known.
For example, Japanese Patent Laying-Open No. 2002-104160 discloses a brake unit used in a drive wheel of an electric car employing an in-wheel motor, in which a brake applied while the car is moving and a parking brake are integrated.
Further, Japanese Patent Laying-Open No. 09-295561 discloses a parking lock unit for an automatic transmission.
However, when a brake mechanism used while a vehicle is moving and a parking brake mechanism are integrated as described in Japanese Patent Laying-Open No. 2002-104160, the vehicle may move when a brake failure occurs.
Further, from a viewpoint different from the above, an electrically driven wheel having an in-wheel motor tends to have an increased temperature within the wheel. Accordingly, in terms of improving heat radiating property, it is preferable to use a disc brake. On the other hand, using a disc brake as a parking lock mechanism leads to an increase in the size of a unit.